How can I make myself start my period!

I had the copper IUD and it fell out when I was on my last period... so I started to track my cycle using this app and cm, well my husband and I used a condom and it broke ( probably from being old haha) so we went to the store to grab plan B because I noticed I was in my fertile week..

BUT now it's been 3 months without a period..

Im not pregnant, I checked multiple times since maybe one day we'd like a 3rd but todays not the day.

so how can I make myself start my period?!?

plus I don't know if it's from the plan B messing with my hormones and making my period be MIA but Ive also gained like 10ish pounds which also sucks because it's hot and humid because it's summer.

any help?